Godot: Broken 3D texture support.

[SIsilicon]

Godot version:
Godot 3.1 alpha

OS/device including version:
Windows 7 64-bit | Intel HD Graphics 4400

Issue description:
I'm creating a port of my volume renderer to 3.1 and noticed this new texture 3D import option. I tried it out along with the new sampler3D uniform in a regular shader. And I get strange results.

Here is a Suzanne 3D texture I made. Prior to Godot 3.1, I emulated the 3D texture sampling of a regular 2D texture. To the edge of the viewport is a pyramid volume. Rendered the same way as the Suzanne volume.

This is after the switch to a 3D texture. The texture has mipmaps enabled.

I disabled mipmaps in this one.

If a reproduction project is required let me know.

[SIsilicon]

I also noticed that the change also happens to pyramid volume despite it's texture not even being 3D. As if all sampler3D's have the same values.

[aaronfranke]

CC @reduz Possibly related: https://github.com/godotengine/godot/issues/20904

[reduz]

@karroffel I noticed we got 3D textures all wrong, will need to fix the API and make a special one for them

[reduz]

apologies, it's my fault.

[SIsilicon]

Thank you for acknowledging this. :-)

[KoBeWi]

Can anyone still reproduce this bug in Godot 3.2.3 rc4 or any later release?

If yes, please ensure that an up-to-date Minimal Reproduction Project (MRP) is included in this report (a MRP is a zipped Godot project with the minimal elements necessary to reliably trigger the bug). You can upload ZIP files in an issue comment with a drag and drop.